1. Field of the Invention
This invention relates generally to the bleaching and sanitizing of fabrics and, more specifically, relates to compositions and methods for effecting such operations with reduced degradation to the fabric and/or dyes contained in the fabrics.
2. Prior Art
It has long been known in the prior art to bleach and/or sanitize fabrics with various chemical compounds which, in aqueous solution, provide a source of available chlorine. The said available chlorine is normally present in solution as hypochlorous acid or hypochlorite ion, depending upon the pH of the solution.
Among the compounds useful for such purposes are polychlorinated cyanurates. Typical polychlorinated cyanurates include sodium dichloro-s-triazine trione, potassium dichloro-s-triazine trione, and sodium dichloro-s-triazine trione dihydrate.
The polychlorinated cyanurates are normally supplied in a dry form; in the presence of sufficient water, they dissolve and react with the water, forming hypochlorous acid (HOCl) or hypochlorite ion (OCl.sup.-) which is responsible for the bleaching and sanitizing actions of the compounds.
In practical use, however, these compounds have the potential to cause extensive damage to the substrates which are being bleached or sanitized, unless they are used according to a prescribed method. This prescribed method of use normally dictates a set of use conditions which eliminate the possibility of the compounds coming in contact with the substrate while in the concentrated form. For example, in the bleaching or sanitization of laundry, normally performed in a washing machine, according to the usually prescribed method of use, the compounds must be dissolved in the wash water prior to the addition of fabrics to guard against the contact of undissolved or partially dissolved particles of the bleaching compound with the fabric being laundered. This is a marked inconvenience, and requires the constant supervision of the operator to insure that no fabric damage occurs. Should the polychlorinated cyanurates or other sources of available chlorine, or formulations containing them, be poured directly onto wet fabrics in the machine under conditions of misuse, extensive damage will occur--in the form of severe dye destruction and/or fabric pinholeing.
In an effort to overcome the damage which thus occurs through the normally expected "misuse" of this type of product, formulators have gone to great lengths to encapsulate the polychlorinated cyanurates, through the use of water soluble film pouches, or agglomeration techniques, in an effort to prevent the direct contact of these compounds with the fabric. These methods are expensive, and, at best, only partially prevent the damage which invariably occurs with misuse.
It has been known for a number of years to utilize in connection with certain types of chlorine producing compositions and solutions, chlorine acceptors which are said to act as stabilizing agents. For example, U.S. Pat. No. 2,988,471 to Fuchs et al, relates to aqueous systems wherein such agents as chlorine, sodium hypochlorite, and calcium hypochlorite, are used to kill pathogenic bacteria and to prevent their growth, e.g. in potable water supplies and swimming pools. It is pointed out that while these aqueous solutions are effective bactericides and are fairly stable in the dark, they have the drawback of decomposing more or less rapidly on exposure to sunlight and in contact with metals such as iron or copper. Accordingly, Fuchs et al teaches that loss of active chlorine in such systems may be substantially reduced by adding to the aqueous solution a material such as cyanuric acid. Fuchs et al also teach the use of these stabilizing materials where the source of active chlorine, as in a swimming pool, is a compound such as sodium dichlorocyanurate.
In Hilton, U.S. Pat. No. 3,431,206, it is observed that polychlorocyanurates, while very useful as bleaching agents in connection with textiles, can cause a substantial loss of textile tensile strength and fading or yellowing of fabrics. This problem is particularly acute with respect to fabrics which have been crease-proofed by use of synthetic polymeric materials, i.e. the so-called "wash and wear" textiles or fabrics. This is said to occur because the chlorine in these bleaching agents attack the -NH groups on the polymer molecule. Hilton et al disclose that this problem can be overcome by use of certain "chlorine acceptors", including cyanuric acid. The patentees teach further, that it is preferred that the aqueous treating solution or suspension employed have a pH in the range from about 0.25 to about 10.5; also in certain embodiments, a pH from 6.5 to 9.5 is described.
Additional prior art pertinent to the present invention, include the following:
Gagliardi et al, U.S. Pat. No. 3,099,625, discloses use of certain nitrogenous organic compounds having in the molecule at least one -NH group whose hydrogen atom is labile and readily replaced by chlorine, as a chlorine acceptor where hypochlorite bleaches are used with "wash-and-wear" textiles or fabrics. PA1 Symes, U.S. Pat. No. 3,350,317, discloses crystalline potassium containing chloro isocyanurate complex compounds and mixtures thereof, having utility in bleaching, sterilizing or disinfecting operations. PA1 Fuchs et al, U.S. Pat. No. 3,145,206, discloses stabilizing dry alkaline metal salts of dichlorocyanuric acid against self-sustaining thermally initiated decomposition, by use, among other possibilities, of cyanuric acid in a dry state. PA1 Fuchs et al, U.S. Pat. No. 3,336,228, disclose a dry laundry bleach which is based upon potassium dichlorocyanurate, a water-soluble alkali metal detergent builder salt in an amount sufficient to stabilize the composition, and a minor amount of an anionic organic surface active agent.
It is noteworthy that in practical use, none of the aforementioned art addresses the problem which is of central concern to the present invention, namely the potential which the aforementioned polychlorocyanurate bleaching agents have to cause extensive damage to substrates which are being bleached or sanitized, when such compositions are not used according to the manufacturer-prescribed methods aforementioned. This difficulty, which is well known to manufacturers and consumers, is sometimes addressed under the heading of "product misuse", and in the instance of bleach compositions of the type to which the present invention pertains, has extreme potential for fabric dye damage.